The ever-increasing demand for smaller sized mobile devices, such as cell phones, digital cameras, etc. has correspondingly triggered a growing need for smaller sized photography modules contained therein. Size reductions may be contributed from various aspects of the mobile devices, which includes not only the charge coupled device (CCD) and the complementary metal-oxide semiconductor (CMOS), but also the optical imaging lens mounted therein. When reducing the size of the optical imaging lens, however, achieving good optical characteristics becomes a challenging problem.
US Patent Publication No. 2011/0299178 disclosed an optical imaging lens constructed with an optical imaging lens having four lens elements, in which the first lens element has negative refractive power and the object-side and image-side surfaces thereof are concave surfaces, and the second lens element has positive refractive power and the object-side and image-side surfaces thereof are convex surfaces, such that the total length of the system approximately equals to 18-19 mm, which is difficult to reduce the length of the optical imaging lens and maintain good optical characteristics, such that which is unfavorable for endeavoring slimmer mobile devices, such as cell phones and digital cameras.
US Patent Publication No. 2011/0188132 and US Patent Publication No. 2011/0188133 both disclosed an optical imaging lens constructed with an optical imaging lens having four lens elements, in which the first and second lens elements have negative refractive power, but the portion of embodiments have excessive air gap between the first and second lens elements, which is difficult to reduce the total length of system and unfavorable for endeavoring slimmer mobile devices, such as cell phones and digital cameras.
Besides, U.S. Pat. Nos. 7,345,830, 7,375,903, 8,253,843, and US Patent Publication No. 2011/0157453 all disclosed an optical image lens constructed with an optical imaging lens having four lens elements, in which the first and second lens elements have positive/negative refractive power arrangement, but the portion of embodiments have excessive air gap between the first and second lens elements, which is difficult to reduce the total length of system and unfavorable for endeavoring slimmer mobile devices, such as cell phones and digital cameras.
How to effectively shorten the length of the optical imaging lens is one of the most important topics in the industry to pursue the trend of smaller and smaller mobile devices. Therefore, there is needed to develop optical imaging lens with a shorter length, while also having good optical characters.